In tune with nature: A singing bird is either at war or in love

Thu, 10 Dec, 2020 - 15:11

Richard Collins

Schoolboys 'take off' their teachers, exaggerating linguistic foibles mercilessly. Gillian Anderson, playing Margaret Thatcher in The Crown, gives The Iron Lady similar treatment. Nor is the ability to recognise vocal sounds confined to humans. When Rico, a border collie living in Dortmund, was just a few months old he began fetching items on hearing them named. By the age of nine, his owners claimed, he had memorised over 200 words.

Psychologists from the Max Planck Institute, in Leipzig, put Rico through his paces. He could, indeed, they found, recognise the names of over 200 objects. On average, he retrieved 37 of 40 items on command, a performance comparable to language-trained parrots and primates.

Whales and birds are the wild world's great vocal communicators. Visibility is limited underwater, so whales 'sing songs', which can be heard tens of kilometres away.

Richard Collins: 'Whales and birds are the wild world's great vocal communicators.'

Likewise, forest-dwelling birds don’t rely on fancy plumage that might not be seen. They broadcast their messages: Birdsong is about warring and wooing. A male announces his territory, warning off rivals and inviting females to join him. Trespassers will be prosecuted.

He soon recognises the songs of his neighbours. When a blow-in arrives and sings, the avian 'neighbourhood watch' goes into overdrive. If song recordings of a stranger are played on a loudspeaker, consternation ensues. Is an intruder trying to rob him of his territory? Will he seduce his partner?

A robin might have several territorial males in his vicinity, each of them constructing songs from dozens of phrases in their repertoires. Nor is the situation stable: Birds die, challengers invade, and divorce is common.

A robin might have several rival males in his territory. Picture: Michael MacSweeney/Provision

Zebra finches (little red-billed residents of central Australia) are gregarious and nomadic. They live and travel in multi-family flocks that can number 100-strong. Mating for life, zebras talk to each other using songs, 'soft contact calls', and 'begging vocalisations'.

Scientists at the University of Berkeley tested the memory capacity of 20 zebra finches. Calls and songs were played to each bird inside a quiet chamber, rewards being offered for recognising particular ones. Birds soon learned which vocalisations delivered the goodies. Then, recordings of other zebras were played to measure how quickly the birds learned them.

Both males and females could remember, on average, 42 'individual signatures' in songs and 'distance calls'. They could locate their mates and relatives by using 'contact calls', even in large flocks. Vocal memories were laid down after as few as five exposures to a particular recording. Each bird not only memorised other birds' calls and songs, but could retain the information for at least a month.

In a paper just published, the authors claim that "the capacity of auditory memory is similar to other forms of avian memory… such as spatial memories in food-caching birds or visual memories in pigeons".